The limitations of observational studies on the treatment of severe sepsis – authors' response

Observational studies usually agree with randomised, controlled trials. It is a logical fallacy, however, to suggest that agreement in one direction implies prediction in the other direction. Observational studies are not scientifically capable of proving or disproving hypotheses such as the efficacy and safety of the treatment of severe sepsis with antithrombin. Observational studies are difficult to analyse and interpret because of the heterogeneity of real-life patient populations, the lack of standardised treatment regimens, the lack of standardised indications for treatment, and the lack of predefined endpoints.